Over the past few years, cars have been trending towards being more lightweight in many ways. Automakers look for ways to reduce a vehicle's weight in order to generate better fuel economy and performance. One of the ways they've done that is largely by replacing engines made of iron with aluminum ones.

For many years, iron engine blocks were the industry standard. Today the majority of all new small engines use aluminum instead, though many large V8 engines still use iron blocks. Aluminum weighs far less than iron -- typically, an aluminum engine weighs half what an iron one weighs. That translates into an overall lighter weight for the car, which means better handling and more fuel efficiency [source: Murphy].

Aluminum does have some drawbacks, however. As a metal, it's not as strong as iron and doesn't hold up to high levels of heat as well. Many early aluminum block engines had problems with cylinders warping, leading to concerns over durability. Those problems have been largely solved, however, and aluminum has clearly asserted itself as the future of engines due to its weight-saving properties.

In this next section, we'll talk about how camshafts have revolutionized engine design.